Wood bending fail - looking for advice

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Bob_H
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Wood bending fail - looking for advice

Post by Bob_H » Mon Oct 19, 2020 4:42 pm

I am a very inexperienced maker, and this is my second time bending wood for a ukulele. First time was Australian maple and I got an outcome I was very happy with. Second attempt was with Tasmanian Blackwood. The photos show the results- from the inside and outside. The wood seemed to become very stiff, and the popped, with a hole opening up.

I’m trying to understand what I did wrong. My theory is that I was too slow, or the iron was too hot, and I cooked the wood, making it too stiff to bend easily There seems plenty of scorching on the inside. When I bent a section that was untouched, it became flexible reasonably quickly, but then I would stop to compare the bend to the template and it would become more difficult to bend.

Any suggestions / observations gratefully accepted. Also, is this savable, or a “teaching moment “?
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Bob Holbert
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56nortondomy
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Re: Wood bending fail - looking for advice

Post by 56nortondomy » Mon Oct 19, 2020 4:51 pm

You could try some ca to glue it back and then make a patch to glue on the inside. Usually b/w bends ok I'm not sure what went wrong for you, I'm guessing your sides were the right thickness, too thick could cause a problem. Wayne

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lamanoditrento
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Re: Wood bending fail - looking for advice

Post by lamanoditrento » Mon Oct 19, 2020 5:50 pm

How thick were your sides? What temperature was your iron? I haven't seen bw crack like that before... Is the side to shape except for the break? If it is then you could possible salvage it. If you still have bending to do in that area, I wouldn't hold out much hope.

Assuming you don't have any further bending to do, I would be attempting to clamp the side to an external mould (ensuring you have clear taped the mould) and then wick in CA. If it holds ok, I would then glue a piece of veneer to the area to sure it up. Or you could do both operations at the same time but perhaps with TB instead of CA.
Trent

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Bob_H
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Re: Wood bending fail - looking for advice

Post by Bob_H » Mon Oct 19, 2020 7:22 pm

lamanoditrento wrote:
Mon Oct 19, 2020 5:50 pm
How thick were your sides? What temperature was your iron? I haven't seen bw crack like that before... Is the side to shape except for the break? If it is then you could possible salvage it. If you still have bending to do in that area, I wouldn't hold out much hope.
Sides are 1.6 - 1.7 mm. Iron was around 200 Celsius. There is more bending to be done in that spot - the pattern has a fairly tight upper bout and I still had waist and lower bout to go - so I doubt a patch will hold, sadly.
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Re: Wood bending fail - looking for advice

Post by johnparchem » Tue Oct 20, 2020 12:06 am

I also bend as hot as my iron goes. I have found as you mentioned the wood becomes plastic relatively quickly with a very hot iron. I have also found it possible to cook the the wood such that it takes a rather brittle set. There is a lot of gluing service so you may be able to use CA. A fix might not look horrible but tt will show where the break is across the grain.

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Bob_H
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Re: Wood bending fail - looking for advice

Post by Bob_H » Tue Oct 20, 2020 10:05 am

I think I can salvage the side at the expense of 5mm in depth to the baritone ukulele that it is intended for - the hole is toward one edge, with the sides being a lot deeper than needed at this stage. I have completely removed the hole and the wood is only 5 mm shallower than the plan specifies, so should not make a big difference.

However, the wood is fairly brittle - I am going to soften it up with some water and try to work more slowly at a lower temperature - still need to get a bigger bend in the location where the break occurred.
Bob Holbert
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Bob_H
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Re: Wood bending fail - looking for advice

Post by Bob_H » Tue Oct 20, 2020 11:30 am

Looking a bit more promising. Slightly lower temperature, more spray water, move more quickly. I’ll let it thoroughly cool / dry and make sure surfaces are good
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lamanoditrento
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Re: Wood bending fail - looking for advice

Post by lamanoditrento » Tue Oct 20, 2020 11:44 am

Well done, glad you were able to save it.

Other may do it differently, but I don't bend that hot. I use a chinese bender from ebay that is in fahrenheit and I set it at 200f which is 93c. Even in the bending machine I normally only get to 300f/148c. I am not shy with water when bending by hand. Water is the medium to transfer the heat.
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Bob_H
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Re: Wood bending fail - looking for advice

Post by Bob_H » Tue Oct 20, 2020 1:21 pm

lamanoditrento wrote:
Tue Oct 20, 2020 11:44 am
Well done, glad you were able to save it.

Other may do it differently, but I don't bend that hot. I use a chinese bender from ebay that is in fahrenheit and I set it at 200f which is 93c. Even in the bending machine I normally only get to 300f/148c. I am not shy with water when bending by hand. Water is the medium to transfer the heat.
Very interesting Trent - that is quite cool - not hot enough to steam the water! Still, results speak for themselves, and your results look pretty good :)
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Mark McLean
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Re: Wood bending fail - looking for advice

Post by Mark McLean » Tue Oct 20, 2020 10:01 pm

I think the problem that you had here is down to the grain orientation of the timber, more than the temperature. The way that it cracked in that rounded pattern suggests to me that it is mainly flat sawn, rather than quartered, and has delaminated between two growth plates which are oblique to the plane of the cut.

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Re: Wood bending fail - looking for advice

Post by Bob_H » Wed Oct 21, 2020 7:28 pm

I think your right there Mark - there was a bit of mixed grain toward the edge of both the sides
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Re: Wood bending fail - looking for advice

Post by Bob_H » Tue Oct 27, 2020 9:25 pm

Coming along nicely now, I think.
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